Colombia has registered 42,706 cases of people infected with Zika, including 7,653 in pregnant women, the country's National Health Institute reported on Saturday.

The latest count represents an increase of 5,695 new cases of the mosquito-borne virus in the last week, including 1,300 in pregnant women.

Although the disease's symptoms are undetectable or mild in most people -- including low fever, headaches and joint pain -- Zika's rapid spread has raised alarms in Latin America because it has been tentatively linked to a serious birth defect known as microcephaly in babies born to women who became infected while pregnant.

Microcephaly is an irreversible condition in which babies are born with abnormally small heads and brains and suffer damage to their cognitive and motor development.

There is currently no cure or vaccine for Zika.

Clinical exams were used to identify 34,464 cases in Colombia, the health ministry said. Laboratory tests confirmed infections in another 1,612, and 6,630 were listed as suspected Zika infections.

Colombia has reported the largest number of cases in Latin America after Brazil, where the outbreak was first detected last year and where 1.5 million Zika cases have been reported.

The health authorities predict more than 600,000 people will be infected with the Zika virus in Colombia this year, and expect more than 500 cases of microcephaly if trends seen in Brazil are repeated.

The Colombian health ministry has also reported three deaths from Guillain-Barre syndrome, a neurological disorder that is also suspected of being linked to the virus.

The World Health Organization (WHO) -- which has declared the rise in Zika-linked birth defects an international emergency -- warns the virus will probably spread throughout the Americas except Canada and Chile.